Enzymes make up a very important class of naturally occuring proteins. Each class of enzyme catalyzes a different kind of chemical reaction. One class of enzymes, known as proteases, are known for their ability to hydrolyze (break down a compound into two or more smaller compounds with the uptake of the H and OH parts of a water molecule on either side of the chemical bond cleaved) other proteins. This ability to hydrolyze proteins has been taken advantage of by incorporating naturally occurring and protein engineered proteases as an additive to laundry detergent preparations. Many stains and soils on clothes are proteinaceous and water-insoluble. Wide-specificity proteases can substantially improve removal of such stains by hydrolyzing the water-insoluble proteins into smaller water-soluble fragments.
Unfortunately, the efficacy level of these proteins in their natural environment, frequently does not translate when applied into the relatively unnatural wash environment. Specifically, protease characteristics such as thermal stability, pH stability, oxidative stability and substrate specificity are not necessarily optimized for utilization outside the natural environment of the enzyme. Moreover cleaning/stain removal performance and fabric care, more specifically wool/silk compatibility are not necessarily optimized.
Considering a specific type of protease (e.g. subtilisins of B. amyloliquefaciens, B. lentus, B. licheniformis etc.), the amino acid sequence of the protease enzyme determines the characteristics of the protease. Changing the amino acid sequence of the protease may alter the properties of the enzyme to varying degrees, or may even inactivate the enzyme, depending upon the location, nature and/or magnitude of the change in the amino acid sequence. Several approaches have been taken to alter the amino acid sequence of proteases in an attempt to improve their properties, with the goal of increasing the efficacy of the protease for cleaning uses such as in the wash environment. These approaches include altering the amino acid sequence to enhance thermal stability, proteolytic activity, oxidation stability, etc. under quite diverse conditions.
Despite the variety of approaches described in the art, there is a continuing need for new effective variants of proteases useful for cleaning a variety of fabrics without damaging the textile properties. It is therefore an object of the present invention to provide detergent compositions substantially free of bleach containing high alkaline protease enzymes combining excellent cleaning/stain removal performance to good wool and/or silk compatibility.